COMMUNITIES AND ECOSYTEMS - WALKING SCAVENGER HUNT - 3 PARTS - FIND THE EXAMPLES OF THE ECOLOGICAL CONCEPTS, FIND THE EXAMPLES OF THE EMBEDDED REVIEW CONCEPTS AND CLEAN UP WHAT YOU FIND ALONG THE WAY.

A few important distinctions

Community vs. Population:

Here the problem lies in the confusion with the way these terms are used in everyday communication. We tend to think of a population on a grad scale and a community in a more local sense. However, in ecology, community is more diverse than a population. Population = collection of organisms of the same species, living in the same area at the same time. Community = collection of populations, also living in the same area at the same timeDecomposer vs. Detritivore vs. Saprotroph:

(Consulting many different sources on this, these terms are used in different hierarchies by different authorities. We are going to go with that consistent with texts authored by IB associates.)

Required terms are detritivore and saprotroph - detritivore ingests non-living organic matter, saprotroph lives on or in non-living organic matter, secretes digestive enzymes into it and absorbs the products of digestion. For our purposes, both of these decompose dead organic matter into smaller compounds, including carbon compounds, which makes them critical to the carbon cycle (see figure and animation below).

This is made a bit more complicated (and more interesting) by the observation that many wood-eating/decomposing insects actually accomplish this feat by working together (symbiotically) with protozoans and bacteria in their gut. More on this in the lab...

click on the image to open animation

Trophic Level Numbering:

This is based upon energy (i.e, calories) flow from "eatee" to "eater," so the first trophic level is always the producers/autotrophs (generally photosynthesis, but there are other forms of energy fixation, such as chemosynthesis, which occurs in ecosystems lacking light energy). The second trophic level is the primary consumers, which is where the confusion can exist.

5.3

POPULATIONS - GROWTH PROFILES

Generalized Growth Curves

World Human Population Projection - 2100

World population from 1800 to 2100, based on UN 2004 projections (red, orange, green) and
US Census Bureau historical estimates (black).

5.2

CLIMATE CHANGE PRESENTATION - FROM NATIONAL ACADEMY OF SCIENCES

ECOLOGY TOK MOMENT...WHAT ABOUT ENDANGERED CULTURES? AS YOU WATCH, THINK ABOUT THE WAY THAT WADE DAVIS USES TERMS FROM TRADITIONAL ECOLOGY IN THE CONTEXT OF ANTHROPOLOGY. HOW DOES THIS MESSAGE LAYER OVER THE DEBATE BETWEEN ENVIRONMENTALISM AND DEVELOPMENT ADVOCATES?